1. Field of the Invention
The present invention directs to an image processing apparatus having a Codec (encoder/decoder) for JPEG 2000 file which performs encoding process and decoding process in JPEG 2000 format.
2. Description of the Related Art
Presently, a JPEG format has been generally used as an encoding format to compress a still image, which compresses an image data using a discrete cosine transform. However, in late years, for the purpose of providing improved compression performance and extended function, development and distribution of a JPEG 2000 format has been promoted, which compresses an image data using a wavelet transform.
Generally, in an image processing apparatus which can process JPEG 2000 file, a processor for JPEG 2000 file is constituted by a hardware device to satisfy request for high speed process of JPEG 2000 file. However, in this case, upper limit of tile size (for example, 128×128 pixels) which can be processed by said hardware device is determined inevitably based on capacity of memory for wavelet transform and inverse transform contained in said processor. Accordingly, since capacity over that of memory for wavelet transform and inverse transform is necessary for the tile size more than the upper limit, the wavelet transform and inverse transform process can not be performed using hardware components.
In case of employing a processor for JPEG 2000 file composed of hardware components, regardless of the above problem, in general, when JPEG 2000 file is generated by a terminal device such as personal computer and the like, tile size is often set large to reduce tile noise which is noticeable on boundary between adjacent tiles or in the vicinity of the boundary. Similarly, it is anticipated that when JPEG 2000 file is generated by an image processing apparatus, it is often required to set a tile size large to reduce tile size.
Conventionally, in case of employing a processor for JPEG 2000 file composed of hardware components, there was no other choice except for abandoning the process itself for JPEG 2000 file having tile size which cannot be processed using memory for wavelet transform and inverse transform. On the contrary, as a technique which can accomplish process for any tile size, it is known that all processes for JPEG 2000 file including wavelet transform and inverse transform are performed without using hardware components as disclosed in Japanese Patent laid-open publication 2002-247580.
However, when all processes for JPEG 2000 file are performed, a prolonged time is required for the processes using only software while being able to process any tile size without limitation.